Electrophotography is a useful process for printing images on a receiver (or “imaging substrate”), such as a piece or sheet of paper or another planar medium, glass, fabric, metal, or other objects as will be described below. In this process, an electrostatic latent image is formed on a photoreceptor by uniformly charging the photoreceptor and then discharging selected areas of the uniform charge to yield an electrostatic charge pattern corresponding to the desired image (a “latent image”).
After the latent image is formed, toner particles are given a charge substantially opposite to the charge of the latent image, and brought into the vicinity of the photoreceptor so as to be attracted to the latent image to develop the latent image into a visible image. Note that the visible image may not be visible to the naked eye depending on the composition of the toner particles (e.g. clear toner).
After the latent image is developed into a visible image on the photoreceptor, a suitable receiver is brought into juxtaposition with the visible image. A suitable electric field is applied to transfer the toner particles of the visible image to the receiver to form the desired print image on the receiver. The imaging process is typically repeated many times with reusable photoreceptors.
The receiver is then removed from its operative association with the photoreceptor and subjected to heat or pressure to permanently fix (“fuse”) the print image to the receiver. Plural print images, e.g. of separations of different colors, are overlaid on one receiver before fusing to form a multi-color print image on the receiver.
Electrophotographic (EP) printers typically transport the receiver past the photoreceptor to form the print image. The direction of travel of the receiver is referred to as the slow-scan or process direction. This is typically the vertical (Y) direction of a portrait-oriented receiver. The direction perpendicular to the slow-scan direction is referred to as the fast-scan or cross-process direction, and is typically the horizontal (X) direction of a portrait-oriented receiver. “Scan” does not imply that any components are moving or scanning across the receiver; the terminology is conventional in the art.
Users require a variety of different surface finishes on prints. For example, a matte finish is typically preferred for black-and-white images, such as text documents, and a glossy finish is preferred for full-color images, such as photographs.
U.S. Pat. No. 5,887,234 to Aslam et al. describes a printer having a first fusing device for producing a low-gloss finish and a second printing device for producing a high-gloss finish. These two fusing devices are separate and do not share components.
U.S. Pat. No. 5,716,750 to Tyagi et al. describes a fixing apparatus for post-treating fused toner to relax residual stress in the toner and adjust the gloss of the finish. Post-treatment methods include reheating and applying a chemical plasticizer to the fused toner. This approach requires additional components, and in some embodiments chemical components, compared to fusing alone.
The approaches of the prior art require additional components and space to selectively provide surface finishes. There is a need, therefore, for an improved method for fusing or glossing toner on a receiver in a space-limited printer.